At least the first 2-4lbs of a gain will be fluid which you should lose in a day or two of coming home. Are you All Inclusive? If so, eat plenty of fruit and yoghurts for breakie, meats and salads for lunch. Often they have fresh food cooked in the evening, like meats or fish. They're bound to be cooked in oil but it wont hurt you. Add loads of veg where you can too.
Cakes/pastries/bread/butter are the foods to be limited if you can manage it. My friend reckons alcohol is "non-sticky fat" therefore lost easily when you return to a normal eating plan.
Ultimately, you have worked hard all year to go on hols and you want to enjoy it, but there's nothing like that sinking feeling when you get back to find out the damage!! Maybe you could indulge at one meal a day, for example one pastry or muffin at breakfast or bread and butter with the evening meal. Drink plenty of water/squash through the day, save your alcohol for the evenings. And limit cocktails!!! I reckon that's where my holiday gain came from!!!
Have a fabulous time xx